Vultures, who can live off rotting meat from carrion that would poison most other animals, not to mention humans, are doing us a favor by ridding the world of significant amounts of dangerous bacteria, researchers say.
Evolution has equipped the vulture with a gut that can kill the bacteria that blossom on the carrion that dominates the birds' diet, and when they feed they're removing a lot of dangerous types of microbes from an ecosystem, the scientists say.
Although researchers have been learning a lot about the human microbiome -- the communities of bacteria that flourish around us, on us and even in us -- little attention has been paid to the microbiome of birds.
"If you're going to study any kind of bird's microbiome, we figured, vultures would be a great place to start," says Gary Graves, the curator of birds for the Smithsonian National Museum of Natural History and co-author of an international study published in Nature Communications. "It's a microbially rich environment, to say the least."
That's because vultures have no qualms about taking the easiest route into a rotting carcass, through the dead animal's anus, which saved them to trouble of having to try and pierce a tough hide with their beaks.
That means they have to survive a double dose of bacteria, both from the rotting flesh and in the fecal matter of the deceased animal.
When the researchers looked at the vultures' microbiome, they were surprised to find the birds have it backwards -- compared to humans, at least.
In humans, the mouth and stomach are host to numerous beneficial bacteria, while there relatively little on our exterior skin.
With vultures, it's just the opposite; their skin -- or at least their faces -- is "dirty" in terms of bacteria, while their guts are surprisingly clean, at least in terms of bacteria found there.
"They're sticking their heads into decaying carcasses, so it's not surprising that their faces have so many kinds of bacteria," Graves said. "But when you get to the lower intestine, it's dominated by a small number of very common bacteria. There's a huge reduction from what they actually consumed."
As they digest the rotting meat they've consumed, the vultures appear to be able to kill off most of the dangerous microbes they take in, the researchers say.
If we can find out how they do that, it might lead to research yielding better antibiotics for humans, they suggest.
Still, benefits for humans are already provided by vultures, courtesy of their dining choices, Graves says.
"People oftentimes don't recognize the enormous ecosystem services that vultures offer to humans," he said. "It's a free, mobile sanitation department. They're discarding and consuming and getting rid of millions of pounds of decaying flesh that could threaten public health."
